Many complex medical interventions rely on the imaging of internal body structures through less invasive means to identify structures and perform procedures without direct visualization. Such indirect visualization means include radiographic imaging such as x-ray fluoroscopy, echocardiography, ultrasound, nuclear magnetic resonance imaging, and tomography. As medical techniques continually evolve to be less invasive, these imaging techniques become more necessary.
X-ray fluoroscopy is used during many percutaneous and natural orifice surgical procedures and intravascular cardiovascular procedures. Percutaneous transcatheter procedures have become the standard of care for many cardiovascular conditions. These procedures rely on x-ray fluoroscopy, coupled with the injection of radiopaque dye to visualize the structures and paths of the circulatory system. Recently, advances have enabled the percutaneous transcatheter placement of valve prostheses.
Accurate placement of a valve prosthesis during transcatheter procedures is a significant challenge that carries substantial risks. During transcatheter aortic valve replacement (TAVR), operators perform Rapid Ventricular Pacing (RVP) to limit the heart motion and improve the chance of an accurate valve deployment. These procedures are done under fluoroscopy. Prior to the placement of the valve prosthesis, Balloon Aortic Valvuloplasty (BAV) is performed to open up the diseased aortic valve. It has been well documented in the early experience with these devices that failure to accurately place the valve prosthesis can result in devastating complications including embolization of the valve into the left ventricle, embolization of the valve into the aorta, and obstruction of the coronary arteries by the valve. These complications are associated with a high incidence of procedure-related death. The geometry of the aortic structures is such that there is only a limited landing zone for the valve to be effective. This limited target zone, when coupled with the movement of the beating heart, creates a difficult procedure with a high complication rate. Advanced vascular disease further complicates the placement.